A retrospective case-note analysis was undertaken of 37 adults with intellectual disability who lived in Leicestershire, England. The subjects were prescribed one of two selective serotonin re-uptake inhibitor (SSRI) antidepressants, i.e. fluoxetine or paroxetine, for perseverative and maladaptive behaviours. The SSRIs proved to be of no benefit for 15 subjects (40%) and led to a deterioration in a further nine cases (25%). However, some reduction of perseverative and maladaptive behaviours was achieved in 13 cases (35%). There was no difference in the responses to fluoxetine or paroxetine.